This invention relates to a apparatus for drawing a side-folded tube over objects piled on the base, the apparatus being provided with a welding and separating device and a device for opening and drawing-over the tube fed in flatly pressed form, this latter device being in the form of four devices each acting on one of the side folds.
In a side-folded tube, not only do the side folds which lie against each other in pairs by their outsides mutually adhere, but the tube parts which lie against each other by their insides also mutually adhere, because of static and heat adhesion. It is known (DT-AS 1,761,895) to dispose guide plates in front of gripping devices which are required to grip a flatly pressed tube, which feed not only the side folds but also the entire tube in a suitable form for gripping. It is also known (DT-GM 918,817) to provide, in combination with gripping devices which are required to grip a flatly pressed tube only at the side folds, a side fold guide in the form of mobile suckers which pull the side folds apart. It is also known (DT-PS 1,940,783) to dispose in front of gripping devices which are required to grip only the side folds, a side fold guide in the form of wedges which push the side folds apart. The withdrawal movement of the side folds which initially lie against each other in pairs may be carried out either at the same time as opening the flatly laying tube (DT-AS 1,761,895, DT-PS 1,938,960, DT-GM 813,256), or before opening the tube (DT-GM 6,918,817, DT-PS 1,940,783, DT-OS 2,026,860). The gripping devices, which serve for opening the tube, are for example suckers (DT-GM 813,256) or clamps (DT-OS 2,026,860), or rods inserted into the tube (DT-PS 1,938,960). In all known apparatus, the tube is fed by a pair of driven feed rollers, disposed in front of the side fold guide. It is also known (FR-PS 2,106,654) to continuously open the tube upwards by mobile clamps gripping the side folds, and to drive the tube downwards by means of gripping devices in the form of bolts gripping into the tube. It is also known to eliminate the side fold adhesion before moving the side folds apart (DT-OS 2,206,273). Finally it is also known (DT-OS 2,315,900) to dispose horizontally slidable clamping devices for opening a tube, and to move them downwards together with rearwardly disposed gripping devices for drawing-over a cover.